The body is a complex machine. It constantly tries to remain in a state of equilibrium. If something shifts this balance, the body sends signals to help us recognise and act on this imbalance. Common signals include thirst (signalling dehydration), tiredness (signalling lack of sleep) and a rumbling stomach (an indication of hunger).
I read a few articles online which had suggested that cravings can be the body signalling nutritional deficiencies. For example, cravings for savoury foods are often thought to be due to a sodium deficiency whereas cravings for chocolate have been linked to a magnesium deficiency.
A craving is defined as a powerful desire for something, not simply confined to food. In the context of substance misuse, a craving can be defined as a strong urge or desire for the use of drugs. This article focuses on food cravings. The difference between a craving and hunger is that: a craving is only satisfied once that particular food has been consumed whereas consumption of any food can alleviate the sensation of hunger. However, quantifying a “powerful desire” in itself is quite subjective and can vary from one person to another. In fact, an interesting article by the BBC (linked below) mentioned that only two-thirds of all current human languages have a word for craving. This suggests that the concept of a craving varies across the world. Despite there being an uncertainty defining cravings, there is a lot within the literature outlining possible mechanisms behind them. A food craving questionnaire developed by Weingarten and Elston for college students in Canada found that cravings are more often reported by females compared to males. 97% of females reported experiencing cravings compared to 68% of males. Given that cravings are common it is important to try and understand the possible mechanisms behind them.
Firstly, I wanted to expand on the notion that cravings are triggered by nutritional deficiencies. It was challenging finding scientific evidence on this topic. One condition which stood out to me when exploring the link between cravings and nutritional deficiencies was pica. Pica is a condition characterised by a craving for and consumption of non-food substances. The most commonly ingested substances include soil or clay, ice and corn-starch. Pica is especially prevalent in pregnant women and children. There is debate on the overall prevalence of pica as many individuals who suffer from the condition may be embarrassed in admitting their cravings. A qualitative study conducted with 76 Mexican-born women who had been pregnant within the last 2 years found that 37% of the participants had engaged with pica (see full article below). There appears to be limited research on this condition and the mechanism of pica is still not fully understood. It is important to try and understand pica more, as consumption of these non-food substances can have adverse effects on the individual or the baby they may be carrying.
One theory behind pica is the nutritional deficiency argument. Iron deficiencies are common in people who suffer from pica. It is thought that pica is a symptom of iron-deficiency rather than the cause of it. There is evidence that treating iron deficiency often resolves the condition.
However, other theories underlying Pica include: individuals actually enjoying the taste and smell of the substance of consumption; it is a behavioural response to certain triggers; as well it being a cultural tradition to consume certain items. Consumption of non-foods is a feature in certain cultures and folk medicine. For example, in certain communities around the world consumption of soil is linked to fertility and reproduction. Therefore, the consumption of soil in these areas may be considered a cultural norm. Various populations have been studied across the world, exploring their different cultural practises in the context of pica. I have included an article below which provides a few more specific cultural examples.
Across cultures, there is variation in the types of foods craved. For example, many studies found chocolate to be the most commonly craved food in Western countries. However, this is not the case in other cultures. A study found vegetable dishes to be amongst the most craved amongst Egyptian males and females (Parker et al 2003). As, there is variation in the foods craved it may suggest that it is not specifically linked to an underlying nutritional deficiency, rather differences in culture. Dark chocolate is high in magnesium (as mentioned above) and so a craving for chocolate is often linked to magnesium deficiency. However, it is not common for people to crave kale, which also contains high levels of magnesium. Furthermore, most of my friends crave milk or white chocolate, rather than dark both of which contain even less magnesium and contain higher amounts of sugar and saturated fat. The BBC article linked below discusses the association between PMS (premenstrual syndrome) and eating chocolate in the West. It may be that during this period women feel it is culturally more acceptable to eat “unhealthy” foods like chocolate. That said, there is work which has found links between cravings and changes in oestrogen and progesterone (hormones released from the female reproductive organs). However, the types of food craved by individuals varied.
Another important mechanism thought to be behind cravings is the “conditioned response.” An experiment (shown below) by physiologist Pavlov explored classical conditioning. In this experiment, the dog is exposed to food, which naturally stimulates salivation. The dog is then exposed to a ringing bell without food, which does not initiate the salivatory response. However, when the bell and food are combined this induces salivation. After a period of time, the bell alone is enough to stimulate salivation. This is called classical conditioning whereby the food is the unconditioned stimulus, the bell is made to become a conditioned stimulus. The salivatory response to food is the unconditioned response and the salivatory response to the bell alone is the conditioned response. Similar effects can be seen in humans. Food-related cues (such as food advertisements of foods, labels, packaging) can act as a conditioned stimulus over time, which then leads to the conditioned response (increased salivation, hunger). Visual food cues can also act on the pleasure-invoking centres of our brain, stimulating the release of feel-good hormones, in a similar mechanism by which drugs work. This can then lead to cravings which can then increase the consumption of food. This is especially problematic in the obesogenic environment in which we live. There is an abundance of advertising as well as easy access to “high energy” food.
Other food cues can be negative emotions and hormone changes. For example, consumption of chocolate results in a subsequent release of serotonin, a feel-good hormone. Therefore people may crave chocolate when they are in a low mood and want to feel uplifted. In this instance, cravings can be conditioned responses to get a hedonic hormonal response even if the individual is not hungry. This pathway is complex and is dependent on different interactions. Simplistically, the conditioned stimulus, in this case, is a negative mood and the conditioned response would be the craving. This highlights the complex emotional response eating can invoke and how individuals may come to depend on eating to suppress negative emotions. It is important to seek help if you think you may be using food as a coping strategy as there are methods you can employ to help reduce food intake as well as improve food selection.
Pavlovian Conditioning
Taken from open.edu
To summarise, it appears as though cravings are highly complex and individualised. They are triggered by an amalgamation of different mechanisms, which are dependent on the particular type of food being craved. This blog focussed on nutritional deficiencies, cultural and behavioural factors. However, there are other factors at play. Overall, I think it is important to listen to what your body tells you whilst also being aware of other possible rationales, other than a nutritional deficiency, which could be triggering the craving. It is important to listen to the needs of your body, whilst differentiating between cravings, due to nutritional deficiencies, versus cravings for foods which psychologically we are drawn to.
If you found reading this article as interesting as I found writing it I have included some relevant useful links if you want more information:
This is a BBC article which describes mechanisms behind food cravings
An interesting article on what Pica is and the current evidence-base for it:
An article outlining the relationship between pica and culture
The study on Mexican-born pregnant women and pica
Lin J.W., Temple L., Trujillo C., et al Pica during pregnancy among Mexican-born women: A formative study. Matern. Child Nutr.. 2015;11(4):550-558. doi:10.1111/mcn.12120
This article goes through the mechanisms of cravings, focussing on the psychological aspect. It also provides possible ways in which to try and combat cravings and eating.
Written by: Adi - Purpose Print
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